Question

solve this question plz. plz. plz

Answer 1

Let the usual speed be x km/h
so according to question,
(1500/x)+[1500/(x+100)]=1/2
》 (1500x + 150000 - 1500x)/[x(x+100)]=1/2
》
$x^{2} + 100x - 300000 = 0$
》
$x^{2} + 600x - 500x - 300000 = 0$
》
$x(x + 600) - 500(x + 600) = 0$
》
$(x + 600 )(x - 500) = 0$
》 x = -600 or 500 km/h

but as speed cannot be negative, so we cannot consider the negative answer so the speed is 500km/h